Eddy current loud-speaker



Jan. 17, 1950 J. w. SUYDAM EDDY CURRENT LOUD-SPEAKER z She ets-Sheet 1 Filed May 22, 1948 Fin-5.1.

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Jan. 17, 1950 J. w. SUYDAM 2,494,782

EDDY CURRENT LOUD-SPEAKER Filed May 22, 1948 v s Sheets-Sheet 2 4 a INVENTOR. BY .fhf. 50x04. 1 :12:43.5 I J adj-ti? flZZOJEAZZY Jan. 17, 1950 J. w. SUYDAM 2,494,782

EDDY CURRENT LOUD-SPEAKER Filed May 22, 1948 3 Sheets-Sheet 3 Mum ELL-l li l IN V EN TOR.

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Patented Jan. 17 1950 UNITED STATES PATENT OFFICE EDDY CURRENT LOUD-SPEAKER Joseph W. Suydam, Blue Point, N. Y.

Application May 22, 1948, Serial No. 28,674

This invention relates to eddy current loud speakers, and aims to provide certain new and useful improvements which lighten the vibratory parts of the device, which permit of the utilization of higher power levels by employing a larger amount of total flux, and which reduce the noise of mechanical rotary parts.

Another object of the invention is the provision of an eddy current loud speaker having continuously rotating magnetic poles whose ma netism is varied by the incoming voice signals, in combination with a hollow unitary metallic cylinder connected at its periphery to a diaphragm and arranged to receive eddy currents whose intensity is governed by the variations in the said magnetism of the rotating poles.

l A still further object of the invention is the provision of a practical, efiicient and compact eddy current loud speaker unit well adapted for installation, public use, and servicing; eddy current loud speakers heretofore produced have not lent themselves to satisfactory public use.

The above as well as additional objects will become apparent in the following description, wherein characters of reference refer to likenumbered parts in the accompanying drawings. It is to be noted that the drawings are intended solely for the purpose of illustration, and that it is therefore neither desired nor intended to limit the invention necessarily to any or all of the exact details of construction shown except insofar as they may be deemed essential to the invention.

Referring briefly to the drawings,

Fig. 1 is a side elevational view of the eddy current loud speaker unit, with parts .broken away to expose the interior, and partly in section.

Fig. 2 is a front elevational view of the same with the casing removed and partly in section on the line 22 of Fig. 1.

Fig. 3 is a sectional view taken on the line 33 of Fig. 1.

Fig. 4 is a sectional view taken on the line 4-4 of Fig. 2.

Fig. 5 is a perspective view of the hollow unitary metallic cylinder per se.

Fig. 6 is a wiring diagram.

Referring in detail to the drawings, the numeral 10 indicates a support or base which in the drawings is shown in upright position. Bolted to the base i0 is an electric motor H whose shaft I2 is provided at both ends with pulleys l3 and M. Belts i5 and It, respectively, are trained about these pulleys.

' The numeral I1 indicates a hollow, light Claims. (Cl. 179-408) weight metallic cylinder having rigid therewith intermediate its length a disc or web l8 which is rotatably mounted on a shaft l9, the latter being rigidly secured by screws 20 to end bells 2!. The end bells 2| provide the ends of a cylindrical housing rather similar in appearance to that of an electric motor, in conjunction with the mid-portion 2-2 of the housing, the said cylindrical mid-portion of the housing being preferably made of a plastic material. The cylinder I1 is, as is obvious, free to vibrate rotationwise on its axis l9. By means of a screw 23 screwed through the cylinder ll into the central web 18 thereof, and a spacer sleeve 24, a driving pin 25 is fixed in a position parallel with a tangent to the cylinder ll. The pin 25 is connected in any desired manner to the loud speaker cone or diaphragm 26.

Two axially spaced spool-shaped magnet members 21, 3! are rotatably mounted on the shaft I9 within the cylinder ll at the sides of the Web It. The outer hubs 2B and 29, respectively, of the members 211 and 3B, are shaped into pulleys. The belt I5 is trained in crossed fashion about the pulley 28, and the belt i6 is trained in open fashion about the pulley 29; thus the motor ll drives the members 2'! and 30 in opposite directions. Each spool 21 and 30 contains a number, usually four, of U-shaped magnets 3| thereby forming eight individual poles onv each of the members 27 and 30; four of these poles are shown for the member 21 at 32, 33,, 34, and 35, and two for the member 30 at 3B, 31, in Fig. .2. Disc-shaped spacers or fillers of non-magnetic material have these magnets 3| im-bedd'ed in them, as shown at 38. Non-magnetic end plates 39 provide the sheaves for the spools 27, 30, and prevent the effects of centrifugal force from loosening the magnets 31.

A coil of wire, 40, is wound around the bases of the four U-shaped magnets 3| of the spool 21, leaving, a circumferential space 42 .around the said bases. A second coil of wire, 4-], is wound around the coil 60. Both these coils are constrained against rotation, that is, held stationary, by means of screws 43 which screw through the housing cylinder 22 and pass through slots 44 in the cylinder I1. In the same manner similar coils i5 and 46 are wound about the bases of the magnets 3| of the spool 30. The coil leads, not shown, may be brought out through the slots 44, or other slots, not shown, from the cylinder l1.

"Securely bedded, usually by adherent-casting in the coil of the cylinder [1.

plastic, not shown, on the interior of the housing cylinder 22, and concentric with but spaced from the cylinder 11, are a plurality of magnetizable bars 41. The purpose of these bars is to provide a continuous magnetic path between all pairs of poles, such as, for example, between the pair 32 and 33, there being no appreciable magnetism carried by one magnetic spool member to the other. The motor H and housing 22 are secured to the base plate In by means of sound-absorbing mountings. The base plate I!) is attached by studs to a sound-absorbing barrier 49 and to the diaphragm mounting ring 5|. Flexibly connected sound-absorbing ducts 52 are provided to air-cool the motor I I. A cover 53, provided with a lining of sound-absorbing material over the rotating members above described, is connected by suitable means with the mounting ring 5!. Bushed openings 55 are conveniently located in the cover 53, through which lead wires, not shown, are fed. The operation of the device is as follows: Coils 40 and 45 are energized by a battery 56 through rheostats 5i and 58, respectively, the currents in these coils being regulated by these rheostats to produce equal magnetism in both spools 21, 30. Because these spools rotate in opposite directions, the eddy current forces tending to rotate the cylinder I! are neutralized, and there is no mechanical pressure on the driving pin 25. a battery 60. Therefore, when sound is impressed on the microphone 59, connected as shown I in Fig. 6, current from the battery is accordingly varied in the coils ll and 46. Owing to the fact that coil Al is connected to augment the magnetism of coil 40 there will be additional drag vor torque on the left-hand end, Fig. 2, of the cylinder I! when added current is sent through However, the same added current flowing through coil it wound in opposition to coil 45 will reduce the drag on the right-hand end Hence, for every variation of electrical input from the microphone 59 or any other desired source there will be a corresponding variation of force on the driving pin 25 and on the diaphragm 26. As in all eddy current loud speakers, the accoustical power output from the diaphragm 26 may be greater than that fed into the electrical input because of the additional power supplied by the motor I Thus a practical, useful and efiicient amplifying eddy current loud speaker has been provided, and obvious modifications in form or structure may be made without departing from the spirit or scope of the invention.

I claim:

1. An eddy current loud speaker comprising an axial support having a rotor mounted thereon, said rotor having peripheral magnets thereon, a hollow metallic cylinder surrounding said rotor and spaced from the poles of sald magnets, said cylinder being axially mounted on said support and being loose thereon, said cylinder having a rigid member secured at one end thereto at a tangent to a circle drawn about the axis of the cylinder, means for rotating said rotor continuously, a speaker diaphragm connected to the other end of said rigid member, and means for varying the magnetism of said magnets.

2. An eddy current loud speaker comprising a rotor having peripheral magnets thereon, a loud speaker diaphragm, a cylinder coaxial with and surrounding said rotor, a rigid member connecting the periphery of said cylinder with said diaphragm, means for continuously rotating said The coils 4| and 45 are connected with rotor, and means for varying the magnetism of said magnets.

3. An eddy current loud speaker comprising a pair of rotors each having peripheral magnets thereon, a loud speaker diaphragm, a cylinder coaxial with and surrounding said rotors, a rigid member connecting the periphery of said cylinder with said diaphragm, means for continuously rotating said rotors in mutually opposite directions, and means for varying the magnetism of said magnets.

4. An eddy current loud speaker comprising an axial support having a pair of spaced rotors mounted thereon, said rotors having peripheral magnets, a hollow metallic cylinder having a transverse web therein, said web being rotatably mounted on said support between said rotors and said cylinder surrounding said rotors, a speaker diaphragm, a rigid member connecting the periphery of said cylinder with said diaphragm, means for continuously rotating said rotors in mutually opposite directions, means for varying the magnetism of said magnets.

5. An eddy current loud speaker comprising an axial support having a pair of spaced rotors mounted thereon, said rotors having radial bars of magnetizable material thereon, a hollow metallic cylinder having a transverse web therein, said web being rotatably mounted on said support between said rotors and said cylinder sur rounding said rotors, a speaker diaphragm, a rigid member connecting said diaphragm with the periphery of said cylinder, means for continuous ly rotating said rotors in mutually opposite directions, said bars having coils surrounding the same and adapted to be electrically energized to magnetize said bars, said bars having additional coils surrounding the same and adapted to have electric currents of varying intensity sent therethrough.

6. The loud speaker set forth in claim 5, having means for locking said coils against rotation.

7. The loud speaker set forth in claim 5, having a shell of magnetizable material surrounding but spaced from said cylinder, said shell having an opening therethrough for the passage of said rigid member.

8. The loud speaker set forth in claim 3, said means comprising coils surrounding said magnets,

and means for energizing said coils with currents of varying intensity.

9. An eddy current loud speaker comprising an axial support having a pair of spaced rotors mounted thereon, said rotors having each at least one U-shaped core of magnetizable material thereon positioned with the arms of the U lying in a plane through the axis of the rotor, a hollow metallic cylinder having a transverse web therein rotatably mounted on said support between said rotors and said cylinder surrounding said rotors, a speaker diaphragm, a rigid member connecting said diaphragm with the periphery of said cylinder, a substantially cylindrical housing having said support secured in the ends thereof and surrounding said cylinder and spaced therefrom, said housing having an opening therethrough for the passage of said rigid member, coils surrounding the bases of said U-shaped magnets, additional coils surrounding said first-named coils, means for rotating said rotors continuously in mutually opposite directions, members extending radially from said housing to the outer surfaces of said additional coils for supporting and positioning said coils, said cylinder having openings having said last-named members passing freely therethrough, either said first-named coils or said second-named coils being adapted to have constant electric currents passed therethrough, the others of said coils being adapted to have varying currents passed therethrough.

10. The loud speaker set forth in claim 9, said housing being made of non-magnetizabl material, and an annulus of magnetizable material supported between said cylinder and said housing.

11. An eddy current loud speaker comprising an axial support having a rotor mounted thereon, said rotor having peripheral magnets thereon, a hollow metallic cylinder coaxial with said rotor and radially spaced from the poles of said magnets, said cylinder being axially mounted on said support and being loose thereon, said cylinder having a rigid member secured at one end thereto at a tangent to a circle drawn about the axis of the cylinder, means for rotating said rotor continuously, a speaker diaphragm connected to the other end of said rigid member, and means for varying the magnetism of said magnets.

12. An eddy current loud speaker comprising a rotor having peripheral magnets thereon, a loud speaker diaphragm, a cylinder coaxial with and radially spaced from said rotor, a rigid member connecting the periphery of said cylinder with said diaphragm, means for continuously rotating said rotor, and means for varying the magnetism of said magnets.

13. An eddy current loud speaker comprising a pair of rotors each having peripheral magnets thereon, a loud speaker diaphragm, a cylinder coaxial with and radially spaced from said rotors, a rigid member connecting the periphery of said cylinder with said diaphragm, means for continuously rotating said rotors in mutually opposit directions, and means for varying the magnetism of, said magnets.

14. An eddy current loud speaker comprising a rotor having magnets thereon, a loud speaker diaphragm, a cylinder coaxial with and radially spaced from said rotor, a rigid member connecting the periphery of said cylinder with said diaphragm, means for continuously rotating said rotor, and means for varying the magnetism of said magnets.

15. An eddy current loud speaker comprising a pair of rotors each having magnets thereon, a loud speaker diaphragm, a cylinder coaxial with and radially spaced from said rotors, a rigid member connecting the periphery of said cylinder with said diaphragm, means for continuously rotating said rotors in mutually opposite directions, and means for varying the magnetism of said magnets.

JOSEPH W. SUYDAM.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,696,303 Hutchison Dec. 25, 1928 2,429,068 McIver Oct. 14, 1947 FOREIGN PATENTS Number Country Date 458,287 Great Britain Dec. 16, 1936 

